In one aspect, the invention pertains to methods of forming semiconductor circuit constructions, such as, for example, methods of forming capacitor constructions. In particular embodiments, the invention pertains to methods of forming capacitor constructions comprising diffusion barrier layers. In other aspects, the invention pertains to solutions of metal-comprising materials, and to methods of storing metal-comprising materials.
As DRAMs increase in memory cell density, there is a continuing challenge to maintain sufficiently high storage capacitance despite the continuing goal to further decrease cell area. One principal way of increasing cell capacitance is through cell structure techniques. Such techniques include three-dimensional cell capacitors, such as trenched or stacked capacitors. Yet as feature size continues to become smaller and smaller, development of improved materials for cell dielectrics as well as the cell structure are important. The feature size of 256 Mb DRAMs is on the order of 0.25 micron, and conventional dielectrics such as SiO2 and Si3N4 might not be suitable because of small dielectric constants.
Chemical vapor deposited oxide films, such as, for example tantalum oxide (Ta2O5), BaTiO3 and SrTiO3 films are considered to be very promising cell dielectric layers. For instance, the dielectric constant of Ta2O5 is approximately three times that of Si3N4. Capacitor constructions have been proposed and fabricated to include the use of one or more of the oxide materials as a capacitor dielectric layer. However, diffusion relative to the oxide materials can be problematic in the resultant capacitor constructions. For example, tantalum from Ta2O5 tends to undesirably out-diffuse from dielectric layers comprising tantalum oxide. Further, materials from the adjacent conductive capacitor plates can diffuse into the tantalum-comprising dielectric layers. In either event, the dielectric properties of the dielectric layer are adversely affected in a less than predictable or an uncontrollable manner.
A method of inhibiting diffusion between tantalum oxide and adjacent materials is to surround the tantalum oxide with a material that constitutes a diffusion barrier layer. Suitable materials for utilization as diffusion barrier layers are materials comprising transition metals (such as, for example, ruthenium, osmium, rhodium, iridium and cobalt), and can include transition metal oxides (such as, for example, ruthenium oxide, osmium oxide, rhodium oxide, iridium oxide and cobalt oxide). The transition metals are typically deposited by chemical vapor deposition (CVD) utilizing metal-comprising precursor compounds. The metal-comprising precursor compounds generally comprise a transition metal coordinated with one or more Lewis base ligands in the form of a complex. Exemplary metal-comprising precursors are (cyclopentadienyl)Rh(CO)2, and (1,3-cyclohexadiene)Ru(CO)3. During a CVD process, the metal-comprising precursors are provided in a reaction chamber with a substrate and subjected to temperature and pressure conditions (and, in some instances, to a plasma or photolysis) to decompose the precursor and cause release of metal from the precursor. The released metal is then deposited on the substrate. A difficulty in utilizing the above-describe metal-comprising precursors in CVD processes is that the precursors frequently decompose prematurely. Such decomposition can occur while the precursors are stored outside the chamber and can result in formation of dimers or molecular clusters of the transition metal precursors. The resulting materials comprising dimers or molecular clusters are generally less volatile than are the original metal-comprising precursors, and accordingly can be difficult to utilize in CVD processes. It would be desirable to develop methods for CVD of metal-comprising precursors which avoid the above-described difficulties.
In one aspect, the invention encompasses a semiconductor processing method of forming a metal-comprising layer over a substrate. A substrate is provided within a reaction chamber, and a source of a metal-comprising precursor is provided external to the reaction chamber. The metal-comprising precursor comprises a metal coordinated with at least one Lewis base to form a complex having a stoichiometric ratio of the Lewis base to the metal. An amount of the Lewis base is provided within the source to an excess of the stoichiometric ratio. At least some of the metal-comprising precursor is transported from the source to the reaction chamber. A metal is deposited from the metal-comprising precursor and onto the substrate within the reaction chamber.
In another aspect, the invention encompasses a method of storing a metal-comprising material. A metal-comprising material is dispersed within a solution. The metal-comprising material comprises a complex having the stoichiometric form (Y)xM(Q)z; wherein M is a metal, Y is a first ligand, x is from 0 to 4, Q is a Lewis base, and z is from 1 to 6. An amount of Q is dispersed within the solution to an excess over the stoichiometric ratio of Q to M in the complex.
In yet another aspect, the invention encompasses a method of forming a capacitor. A first capacitor electrode is formed over a substrate. A diffusion barrier layer is formed proximate the first capacitor electrode. A dielectric layer is formed. The dielectric layer is separated from the first capacitor electrode by the diffusion barrier layer. A second capacitor electrode is formed. The second capacitor electrode is separated from the first electrode by the dielectric layer. The forming the diffusion barrier layer comprises the following steps. The substrate having the first capacitor electrode thereover is provided to within a reaction chamber. A source of a metal-comprising precursor is provided external to the reaction chamber. The metal-comprising precursor comprises a metal coordinated with one or more Lewis bases to form a complex having a stoichiometric ratio of the Lewis bases to the metal. At least some of metal-comprising precursor in the source is a liquid. A gas is provided, and an amount of at least one of the Lewis bases is distributed within the gas. After the Lewis base is distributed within the gas, the gas is passed through the liquid metal-comprising precursor of the source. At least some of the metal-comprising precursor from the source is transported to the reaction chamber with the gas. A metal-containing film is deposited from the metal-comprising precursor onto the substrate.